what happens when carbon disulphide is added to the mixture of heated iron filings and sulphur?

When the mixture of iron and sulphur is heated, iron(II) sulphide (also known as ferrous sulphide) is formed. In other words, it becomes iron(II) sulphide and is NOT the mixture of iron and sulphur any longer.

When carbon disulphide is added to the cooled iron(II) sulphide, there would be no observable change because there is no reaction.

CS2 dissolves the sulfur that has not reacted.

You are suppose to let the heated mixture COOL and then grind it to a powder before adding the CS2 ... CS2 has a low vaporization point and will burst into flame .. IE it spontaneously combusts.